The present invention relates to valves used to restrict the direction of flow in process piping. More specifically, the present invention relates to a check valve which can be inserted between two standard flanges in any process piping system. Yet more specifically, the present invention relates to a simple, low cost, easily installed, replaceable check valve particularly adapted for sanitary piping systems used in the food, dairy, pharmaceutical, and biotechnology industries.
The use of check valves in sanitary piping systems is well known in the prior art. Although prior devices have been designed to accomplish the purpose of maintaining unidirectional flow while meeting the constraints of sanitary piping practice, each possesses disadvantages which are overcome in the present invention. In fact, many utilize a similar design and manner of operation which is significantly different from the design and manner of operation of the present invention.
There are several important criteria for selecting a check valve for use in a sanitary piping system. Perhaps the most important is that the valve be drainable, such that the valve does not include any physical features which would retain permanent puddles of water or liquid. While it is sometimes inevitable that a puddle of liquid may be formed when a valve is in the closed position, due to the orientation and flow direction of the piping into which the valve is mounted, it is critical that this puddle disappear when the valve is opened during the sterilization operation. Full drainability is a cardinal rule in the design of sanitary piping systems.
In a typical sterilization operation, steam is flowed through the sanitary piping system, raising all internal surfaces to a temperature of at least 250° F. (121° C.) and a corresponding saturation pressure of approximately 15.2 PSIG, and holding them at this temperature and pressure for a minimum of 30 minutes. Of course, other time-temperature profiles are used in different circumstances, but this is one of the most common. If a puddle of liquid were to be retained anywhere within the piping system, this puddle may not attain a sufficient time-temperature profile during sterilization to kill any potential contaminating organisms, and as a result the system may not be sterile. Lack of sterility can cause the loss of a entire batches of product and large amounts of wasted production time and money.
Implicit in the drainability criteria is also the requirement that the valve be capable of operating through repeated cycles of production and steam sterilization. It is noted that often a single sequence of the cycle involves multiple steps, for example steam sterilization to production to cleaning to steam sterilization. Once a system has been sterilized, no pipe fittings can be disconnected to replace a component without compromising the sterility of the entire system. Further, if a system is contaminated during production, no pipe fittings can be disconnected to replace a component until another sterilization has been completed without jeopardizing the safety of personnel.
An additional criteria for selecting a check valve for sanitary piping systems is that the valve be easily installed, maintained, and if necessary, replaced. A bonus feature would be the ability to readily retrofit the valve into existing sanitary piping systems. Because sterility is such a premium requirement, it is routine for all of the elastomer components of a sanitary system to be replace on a regular preventive maintenance schedule. Thus, a valve which is not easily accessible for maintenance or replacement would be a liability.
A further criteria for selecting a check valve for a sanitary piping system, or for any piping system, is noiseless operation. Often, when there is barely sufficient forward flow to overcome the cracking pressure of a check valve, the valve will flutter rapidly between its closed and open states, as pressure accumulates and is then relieved upstream of the valve. When both the stationary valve seat and the moving valve plug are made of metal or another hard material, this rapid flutter will inevitably result in chattering, creating an annoying noise for nearby workers and possibly doing harm to the components of the valve.
Yet a further criteria for selecting a check valve for a sanitary piping system, or for any piping system, is that the valve provides a simple visual indicator or means to ascertain that the valve is in fact installed, that the valve is installed in the correct flow direction, and that the valve is installed so that it is fully drainable. Some of the sanitary check valves currently on the market may be installed in between sanitary flanges but once they are installed there is no visual or other indication, other than breaking the flange connection and pulling the pipes apart, to know that the valve is present or that it is facing in the correct flow direction.
The check valve of U.S. Pat. No. 2,170,478 [Long], while not designed for sanitary applications, discloses a basic physical design that is common in the prior art. This valve includes a spring loaded valve plug which moves longitudinally inside a pipe with respect to a stationary valve seat in combination with a stationary flow-through mounting arrangement which anchors the spring.
The check valve of U.S. Pat. No. 4,138,338 [Skoli] discloses a similar physical design whereby the combined stationary valve seat and flow-through mounting yoke is designed to be held in place between two flanges in a piping system. Although the mounting system is of a more sanitary design, this check valve includes a spring and a threaded nut and bolt arrangement which have crevices for contamination to collect. This valve, however, does provide a visual indicator of flow direction.
U.S. Pat. No. 5,033,503 [Horton] discloses a check valve which is commercially available as the “Style SCV Sanitary Cartridge Valve” from Check-All Valve Manufacturing Co. This valve is retained between two mating pipe flanges by an annular shoulder on the valve seat holder and features a spring loaded plug which moves longitudinally with respect to the valve body to open and close a flow passage. The design includes o-rings intended to seal between the valve seat holder and the inside wall of the piping, to prevent fluid from leaking out between the flanges and to eliminate the need for a flange gasket. This creates two problems. First, there is an annular crevice between the valve seat holder and the inside pipe wall, extending inwardly from each end of the valve back to the corresonding o-ring, which is not readily cleanable and sterilizable. Second, in practice, these o-rings do not seal well, since the internal surface of the pipe or tube is not design for this type of application and is therefore not of sufficient uniformity. The resultant leakage past the o-rings creates either a leak out of the flange or necessitates the addition of a flange gasket. Further, any process fluid leaking behind the o-rings presents a much more serious risk of contamination due to the complete inability to clean and sterilize this area bounded by the pipe wall, the valve body, the o-rings, and the flange gasket. Additionally, this valve provides no visual indicator of flow direction or that it is in fact installed at all, and in practice it is sometimes required to pull apart the mating pipe ends just to verify the existence and proper installation of the valve.
U.S. Pat. No. 6,039,073 [Messick] and U.S. Pat. No. 6,152,171 [Messick] disclose a valve commercially available as the “Style 3SC Sanitary Check Valve” from Check-All Manufacturing Co. This valve includes a different plunger from the “Style SCV” valve and is specifically intended for installation between sanitary style flanges of the tri-clamp design. However, the “Style 3SC” valve includes the same o-ring configuration as the “Style SCV” valve and therefore suffers from the same disadvantages and problems. This valve, too, lacks any visual means to indicate that it is installed at all, or that it is installed in the correct flow direction.
Check-All Manufacturing Co. also markets another check valve for mounting between sanitary flanges as the “Style SIV Sanitary Insert Valve”. This check valve includes a similar plunger to the other Check-All valves. The mounting arrangement of this valve includes an annular shoulder molded into the valve seat holder which also acts as the tri-clamp flange gasket, eliminating the need for o-rings. However, this valve also includes a shroud around the valve plug having an outside diameter almost as large as the inside diameter of the pipe or tube into which it fits, thus creating a potential crevice with its inherent cleaning and sterilization problems. Also, this valve lacks any visual means to indicate that it is installed at all, or that it is installed in the correct flow direction.
Other commercial check valves are on the market. The “W45” check valve from Waukesha Cherry-Burrell is designed for sanitary service and includes a valve body which inserts in-line between two sanitary flanges as a section of tubing with varying diameter. The valve body has sanitary flanges at either end and a third sanitary flange pair in the center to retain a stationary valve guide. A spring-loaded valve plug moves longitudinally with respect to the valve guide and seats on a tapered portion of the inside wall of the valve body. To create a flow passage when the valve plug is in the open position, the valve body includes a section of larger diameter than the prevailing tubing in which it is mounted, thus creating a potential low point if this valve were to be mounted in horizontal piping. Therefore, this valve design must be mounted in vertically piping in order to be fully drainable for sanitary purpose, in accordance with the mounting instructions of the manufacturer. Lumaco markets a sanitary check valve that is almost identical in design to the “W45” of Waukesha Cherry-Burrell.
The “DSV Sanitary Check Valve” by DFT Incorporated is sold in both a vertical and a horizontal mounting configuration. This valve includes a valve body which inserts in-line between two sanitary flanges as a section of tubing with varying diameter which retains one end of a flow-through mounting yoke and valve guide. The valve body has sanitary flanges at either end and a third sanitary flange pair in the center to retain the other end of the mounting yoke and to create a valve seat. A spring-loaded valve plug moves longitudinally with respect to the valve guide and mounting yoke. To create a flow passage when the valve plug is in the open position, the valve body includes a section of larger diameter than the prevailing tubing in which it is mounted. In order to make the horizontal mounting design drainable, the outlet portion of the valve is offset in a downward direction from the inlet portion of the valve so that the outlet section is the low point. Therefore, for drainability, this valve can only be mounted in downward-pitched horizontal piping and not in upward-pitched horizontal piping.
Accordingly, it is an object of the present invention to provide a sanitary check valve adapted for mounting between any flanges, and particularly between sanitary flanges, in an existing piping or tubing system. It is another object of the present invention to provide a sanitary check valve that is fully drainable when mounted in piping pitched at any orientation, including vertical, near horizontal, or any angle in between. It is a further object of the present invention to provide a sanitary check valve that contains no crevices or physical features which may capture contaminants, so that the valve is cleanable by conventional flow-through CIP (clean-in-place) methods and sterilizable by conventional flow-through steam SIP (sterilize-in-place) methods. It is still a further object of the present invention to provide a sanitary check valve which includes a simple visual indicator that the valve is in fact installed, that the valve is installed in the correct flow direction, and that the valve is installed so that it is fully drainable.
It is yet another object of the present invention to provide a sanitary check valve that is durable and inexpensive compared with those presently on the market. It is yet a further object of the present invention to provide a sanitary check valve that is easily replaceable during routine preventive maintenance. It is still a further object of the present invention to provide a sanitary check valve that may be fabricated from materials already widely accepted and used in the food, dairy, pharmaceutical, and biotechnology industries.
Other objects will appear hereinafter.